When you have done some comparison and picked out a well-formulated food, make sure you allow ample time for your pet to make the transition from their current food to the new one. Normal bacteria in the intestine help your pet digest food. A sudden change in food can lead to changes in the number and type of these bacteria, making it harder for food to be digested, and resulting in intestinal upset. To avoid problems, switch to a new food slowly, over the course of at least 7-10 days. Start by mixing 25% new and 75% old food, and feed that for at least 3 days. If all goes well, go to 50% of each type of food for 3 days, then 75% new and 25% old for 3 days. By now, your pet should be ready to eat only the new food. If problems occur, consult your veterinarian for advice.

After you have done all you can to make sure a food is nutritionally sound, take a look at your pet after they have been on the new food for at least a month. Bright eyes, a shiny coat, good weight (not too thin or overweight), and good energy will let you know you are doing a good job with your pet's nutrition.